1. Field of the Invention
The present invention relates to an apparatus for editing documents such as a computer typesetting system (CTS), a desk-top publishing system (DTP), a documentation workstation, or a word processor.
2. Description of the Related Art
The inventor of the present invention knows that there are document editing apparatus capable of editing documents i.e., inserting or deleting a character string and/or a frame for enclosing a character string as well as changing sizes of characters or frames.
However, the above-mentioned document editing apparatus has to rebuild a composition of other characters rather than the target characters with the insertion, the edition or the change of the sizes of the target characters.
In a case that one character is inserted, the above-mentioned document editing apparatus rebuilds the locations of the inserted characters as well as the character string after the inserted characters in the line (change the displayed locations of the characters). For instance, one or more characters are overflown out of the line, the above-mentioned document editing apparatus performs a change of the displayed locations of all the characters after the inserted character in the paragraph. As a result of the change, the lines are increased and the apparatus performs a change of the displayed locations of all the characters after the inserted character in the paragraph.
The above-mentioned document editing apparatus performs of temporarily painting the characters in white on the display area to be changed for deleting those characters and to display font raster images read out of an IC memory or an external storage device at the new locations on the display determined by the edition.
The above-mentioned document editing apparatus is designed to change the displayed locations of all the changed characters resulting from the edition. Hence, the apparatus has a disadvantage that it requires a long time (response time) between a time period when an operator gives an edition indication and when the edited result is terminated. In particular, the apparatus for a high-level editing which is capable of handling many kinds of fonts and many character sizes cannot actually have all the font raster images including less frequently-used fonts in an internal storage device such as an IC memory for the purpose of making economical use of the hardware. This type of apparatus, therefore, often has the font raster images which are stored in an external storage device or changed as vector fonts like outline fonts. In order for this type of apparatus to display the characters, it is necessary to read the font raster images from the external storage device and to expand or reduce the font raster images or to develop the vector fonts for obtaining the raster images. It results that the high-level document editing apparatus requires a larger load and a longer response time on the display system in order to change the displayed locations of the characters.
Moreover, another type of the above-mentioned document editing apparatus which is capable of supporting a multi-window function is arranged to save the displayed part hidden under another window as raster images in the storage device and to display the stored raster images at a time when it restores the original image for the purpose of reducing a response time. The above-mentioned apparatus, however, can not improve a disadvantageous longer response time, because it serves to read the font raster images from the IC memory or the external storage device and to display the font raster images at the new display locations resulting from the edition.